The L86 LSW makes its first appearance as a Light Machine Gun in Call of Duty: Modern Warfare 2. It appears in both the campaign and multiplayer modes with a 100-round drum magazine, iron sights and the carrying handle. Uniquely, when the ACOG Scope attachment is equipped, it takes the appearance of the British 'SUSAT' Scope.

In the campaign, the L86 LSW makes its only appearances in the campaign mission "Loose Ends", and the Special Ops mission Estate Takedown. Three of them (complete with SUSAT sights) can be found in the room next to the kitchen on the first floor of the house. Another L86, with Iron Sights only, can be found in the basement of the weapon and ammo cache armory. It is extremely useful as it has LMG firepower and magazine size without the long reload time associated with an LMG. Unlike its multiplayer counterpart, the campaign version L86 LSW has near-zero recoil.

The L86 is one of two pre-unlocked light machine guns, and the primary weapon for the default Overwatch class, which includes a Red Dot Sight and a Grip.
The L86 LSW has one of the highest damages per second of any weapon in the game. At close range, its damage per second is beaten only by the shotguns, the G18 and MP5K, and is equal to the TAR-21 and the PP2000. The L86 LSW has the highest damage per second at long range out of all the automatic weapons, and is able to kill in two shots with Stopping Power or three shots without it. But the L86 also has the highest recoil of all the LMGs by far, making it difficult to use at longer ranges unless firing in short bursts. The L86 has the second fastest reload time of the LMGs, after the AUG HBAR, and benefits greatly from Reload Canceling.

L86 has heavy recoil when firing in full-auto, and its iron sights are generally disliked, as they block the target at long range and will suffer heavily from muzzle flash. As a result, it is most commonly used in conjunction with the Bling perk, with a Grip and sight attachment. Like other LMGs, it also suffers from a slow ADS draw time, although this can easily be mitigated with the Sleight of Hand Pro perk. Firing single or double shots can make the L86 much more accurate at longer ranges and make it easily capable of racking up kills on maps with tight alleyways where suppressing fire is often needed. If the player chooses to add a sight to the gun, the SUSAT scope is a good candidate, as although it does increase recoil slightly, its sight is much clearer than the iron sights, making it more effective at long range, while raising ADS to the point where muzzle flash is not even seen, let alone a problem. The alternative choice is the Holographic Sight, which offers the most precision at the expense of some muzzle flash.

Due to the extremely high damage per second of the L86 it can be surprisingly effective in CQB, certainly the most effective of all the LMGs. Compared to most CQB weapons it sacrifices fast handling for tons of ammo, allowing the gun to excel in engaging large numbers of enemies. Sleight of Hand Pro helps hugely in such situations, as the slow ADS time when compared to assault rifles and SMGs can otherwise be crippling. Additionally, with Sleight of Hand the reload time of the L86 with reload canceling is as low as many assault rifles. Due to the rarity of needing to reload, having a secondary as a backup is less necessary than on most guns, freeing up this space for launchers or One Man Army. Finally, the very high bullet penetration the L86 shares with all LMGs can give it an edge shooting through walls over most weapons particularly on maps like Favela or Scrapyard.

The Silencer reduces damage, but still makes the L86 LSW arguably the best stealth LMG since the other four LMGs either have a faster fire rate but lower damage (M240), or the same damage and a slower rate of fire (the RPD and AUG HBAR) compared to the L86. However, one should keep in mind the M240 and MG4 have glitched silencers; the red dot still shows on enemy radar. As stated it suffers from having higher recoil than any other LMG, meaning at longer ranges burst-firing or semi-auto firing is required to kill where the others would be able to fire full-auto.

When fitted with the Heartbeat Sensor, while in ADS, the player can still view all but the very bottom edge of the Sensor screen. In conjunction with a grip, it can make a very good mid-range support weapon.

The L86 was supposed to be an L85 rifle at one point in Call of Duty: Modern Warfare 2, as the L86's texture sheet has the L85's 30-round magazine on it. The campaign pick-up icon also has the L85's 30-round magazine. The L86's kill icon in multiplayer is still an L85, giving further evidence that the L86 was once an L85. Also, the maximum ammunition amount in the campaign is 420, which is divisible by 30, the usual Assault Rifle magazine size, further suggesting it was the L85 earlier in development.

"Possessing the highest rate of fire in its class, the L86 LSW suppresses enemy targets with a relentless stream of bullets. Its heavy frame noticeably slows mobility, and high recoil combined with low accuracy makes pinpoint targeting difficult. Find a defensible position, get low, and tear down incoming targets from afar."

The L86 LSW is featured in Call of Duty: Modern Warfare 3. It is similar in appearance to the Call of Duty: Modern Warfare 2 variant, but with new iron sights using an L85 carry handle as the rear of the sight, and the removal of the rear-fitted grip. In the Redemption trailer, it is shown briefly with the Call of Duty: Modern Warfare 2-styled Red Dot Sight, but was unavailable in-game, being replaced in that part with the carry handle variant.

The L86 LSW is found in the mission "Bag and Drag" with a Red Dot Sight in the blue van that Delta Force uses to chase down Volk. It is also found in the mission "Stronghold". The L86 LSW on Stronghold uses the Modern Warfare 2 model as well as the SUSAT scope.

The L86 LSW is unlocked at Level 4 in Call of Duty: Modern Warfare 3's multiplayer. In several areas, it is almost statistically the opposite of its Call of Duty: Modern Warfare 2 counterpart; while in Call of Duty: Modern Warfare 2 it had high damage and high recoil, in Call of Duty: Modern Warfare 3 it features a relatively high rate of fire, lower recoil, and moderate damage. It has slight horizontal and vertical weapon recoil, causing the sights to jump off target when fired. While this will not cause problems in close range, it can make engaging targets at long range difficult.

Compared to the other LMGs, the main strengths of the L86 are the fast reload time (beaten only by the MG36), the fast rate of fire (beaten only by the MK46) and the lowest recoil among all the LMGs. When coupled with the Grip attachment or the Kick proficiency, the weapon's bullet spread improves greatly, although the weapon will still show considerable kick. All combined, the L86 is capable of a large volume of accurate fire with minimal interruption from reloading. If the Grip and Kick proficiency are used together, this weapon will be capable of firing in long bursts (around four to five bullets) on targets at ranges where players would consider using sniper rifles. Using Rapid Fire is very lethal in close range, but firing fully automatically for a consistent time without either Kick or Grip will result in extremely high weapon recoil.

Its minimum damage was increased via hotfix, and now it only needs three bullets to kill at all ranges, even when using a silencer. This, along with its high rate of fire and low recoil, makes the L86 LSW one of the most versatile LMGs.

The Thermal Scope removes the weapon kick, the weapon's main downside, and turns it into the most accurate automatic weapon in the game. Also, when using the Grip attachment, reload time is increased to what it was in Call of Duty: Modern Warfare 2, although add time is unaffected.

The L86 LSW is available in Survival Mode at level 41 and costs $7000. Compared to other LMGs, it is rather versatile due to its fast reload speed and high fire rate, but due to its low damage, is beaten in almost every aspect by the MG36. Adding the Grip is highly recommended for the L86 as its recoil is rather high. When using the grip, its recoil tends to walk upward, but this can be remedied by pushing slightly down with your mouse/R-stick.

The Silencer is not centered on the LSW's barrel. It appears to be mounted slightly below the muzzle.

In the campaign, Special Ops and multiplayer, when turning, the L86 stays at the same angle as when the player is still. However, this is different from most of the other weapons. In multiplayer, most weapons rotate on the muzzle, whereas in the campaign, most weapons act like the L86 does in multiplayer.

When using a grip with this weapon, the players thumb is on the front of the grip along with his other fingers.

The Create-a-Class model, the third person model, and the HUD model of the L86-LSW have a grip behind the drum mag.

When reloading, the grip increases reload time; however, only the motions are slowed down, since the time for the bullets to be refilled remains the same as without the grip. This means reload canceling works.